As is well known, a magneto generator is comprised of a magnet rotor that produces a magnetic field by mounting a permanent magnet to a rotor yoke, and a stator including an armature coil wound around an armature core having a magnetic pole portion facing a magnetic pole of the magnet rotor.
The magnet rotor is mounted to a rotational axis of a prime mover, and the stator is secured to a predetermined mounting portion provided on a casing or a cover of the prime mover, so that the magnetic pole portion provided on the armature core faces a magnetic pole portion of the magnet rotor with a predetermined gap therebetween.
In the magneto generator, the magnetic field of the magnet rotor is produced by the permanent magnet, and thus the magnetic field cannot be controlled by a method similar to that for a magneto generator having field winding to control an output of the magneto generator.
The applicant proposes, as described in Japanese Patent Application Laid-Open Publication No. 11-46456, a generating device that is comprised so as to apply an AC control voltage to an armature coil from voltage accumulation means such as a battery or a capacitor provided on a load side via an inverter, wherein a phase of the AC control voltage is changed to change a magnetic flux linking the armature coil and change an output characteristic of a magneto generator.
In the magneto generator, when an AC control voltage having the same frequency as an induced voltage of the armature coil is applied to the armature coil to change a phase angle of the AC control voltage to a delayed side relative to a phase of a no-load induced voltage of the armature coil, an output of the magneto generator can be generally increased, and when the phase angle of the AC control voltage is changed to an advanced side, the output of the magneto generator can be reduced. The phase angle of the AC control voltage relative to the phase of the no-load induced voltage of the armature coil is referred to as a “control angle.”
Thus, depending on whether the output of the magneto generator (an output voltage or an output current) is lower or higher than a target value, the control angle is changed to the delayed side or the advanced side to allow control for matching the output of the magneto generator with the target value.
Such control that a generating device is comprised so as to apply the AC control voltage to the armature coil of the magneto generator from the voltage accumulation means provided on the load side via the inverter, and the phase angle of the AC control voltage is controlled to adjust the output of the magneto generator is referred to as “drive control”, which means controlling the output of the magneto generator while driving the magneto generator from the load side.
The generating device proposed in Japanese Patent Application Laid-Open Publication No. 11-46456 includes: a magneto generator having a magnet rotor with a magnetic field, and a stator having an armature coil wound around an armature core with a magnetic pole portion facing a magnetic pole of the magnetic field, the magnet rotor being driven by an internal combustion engine; an AC/DC conversion circuit having an AC/DC converter that converts an m-phase AC output voltage obtained from the magneto generator into a DC voltage to apply the DC voltage to voltage accumulation means such as a battery or a capacitor, and an inverter that converts a voltage across the voltage accumulation means into an AC voltage to apply the AC voltage to the armature coil; and a controller that controls the inverter so as to apply an AC voltage having the same frequency as a present induced voltage of the armature coil as an AC control voltage to the armature coil from the voltage accumulation means via the inverter.
The controller controls the inverter so as to apply the AC control voltage having the same frequency as the induced voltage of the armature coil to the armature coil from the voltage accumulation means such as the battery provided on the load side via the inverter when the output of the magneto generator deviates from the target value, and change the phase angle of the AC control voltage to the advanced side or the delayed side relative to a present phase angle to control and bring the output of the magneto generator close to the target value. Thus, changing the phase angle of the AC control voltage to the advanced side or the delayed side relative to the present phase angle is equivalent to controlling the control angle of the AC control voltage.
As a regulator that controls an output of a magneto generator, a short circuit type regulator has been often used such that the output of the magneto generator is short-circuited when an output voltage exceeds a target value. However, when the short circuit type regulator is used, a high short circuit current passes through an armature coil when the output of the magneto generator is adjusted, which may increase heat generation from the armature coil or heat generation in a switch element that constitutes the regulator.
On the other hand, if the output of the magneto generator is adjusted by drive control, the output of the magneto generator can be adjusted without passing the short circuit current, which can prevent an increase in temperature of the armature coil of the magneto generator or an increase in temperature of the switch element during adjustment of the output.
However, it is revealed that when the control angle is changed to the delayed side at a fixed rotational speed of the magneto generator, and the control angle is delayed to some extent, the output of the magneto generator stops increasing, and the output of the magneto generator decreases for further delay. Similarly, it is revealed that when the control angle is changed to the advanced side at a fixed rotational speed of the magneto generator, and the control angle is advanced to some extent, the output of the magneto generator stops decreasing, and the output of the magneto generator increases for further delay.
Therefore, when there is a large difference between the output of the generator and the target value in the drive control, and the control angle is changed to the delayed side, a relationship between a changing direction of the control angle and a changing direction of the output of the magneto generator is reversed during the control to reduce the output of the magneto generator with the delay of the control angle. Such a state causes the control angle to continue changing to the delayed side, and prevents the output of the generator from converging to the target value. Similarly, when the control angle is advanced to control and restrain the output of the magneto generator, excessively changing the control angle to the advanced side causes an increase in the output of the magneto generator with the change of the control angle during the control, and prevents the output of the generator from converging to the target value.